Howard Griffiths

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Carbon isotope discrimination during photosynthetic CO2 assimilation has been extensively studied and rigorous models have been developed, while the fractionations during photorespiratory and dark respiratory processes have been less well investigated. Whilst models of discrimination have included specific factors for fractionation during respiration (e)(More)
We revisit the relationship between plant water use efficiency and carbon isotope signatures (δ13C) of plant material. Based on the definitions of intrinsic, instantaneous and integrated water use efficiency, we discuss the implications for interpreting δ13C data from leaf to landscape levels, and across diurnal to decadal timescales. Previous studies have(More)
The advent of saturated molecular maps promised rapid progress towards the improvement of crops for genetically complex traits like drought resistance via analysis of quantitative trait loci (QTL). Progress with the identification of QTLs for drought resistance-related traits in rice is summarized here with the emphasis on a mapping population of a cross(More)
A method of monitoring and collecting CO2 samples in the field has been developed which has been used to study both temporal and spatial variations in canopy CO2 isotopic signatures in two contrasting tropical forest formations in Trinidad. These have been related to vertical gradients in the carbon isotope ratio (δ13C) of organic material in conjunction(More)
The occurrence, activity and plasticity of the CAM pathway is described from an introductory viewpoint, framed by the use of the four "Phases" of CAM as comparative indicators of the interplay between environmental constraints and internal molecular and biochemical regulation. Having described a number of "rules" which seem to govern the CAM cycle and apply(More)
There has been much interest in the chloroplast-encoded large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) as a target for engineering an increase in net CO(2) fixation in photosynthesis. Improvements in the enzyme would lead to an increase in the production of food, fiber, and renewable energy. Although the large subunit contains(More)
The magnitude of fractionation during photorespiration and the effect on net photosynthetic (13)C discrimination (Delta) were investigated for three Senecio species, S. squalidus, S. cineraria, and S. greyii. We determined the contributions of different processes during photosynthesis to Delta by comparing observations (Delta(obs)) with discrimination(More)
The ability to concentrate CO₂ around Rubisco allows C₄ crops to suppress photorespiration. However, as phosphoenolpyruvate regeneration requires ATP, the energetic efficiency of the C₄ pathway at low photosynthetic flux densities (PFD) becomes a balancing act between primary fixation and concentration of CO₂ in mesophyll (M) cells, and CO₂ reduction in(More)
Concentration and isotopic composition (δ13C and δ18O) of ambient CO2 and water vapour were determined within a Quercus petraea canopy, Northumberland, UK. From continuous measurements made across a 36-h period from three heights within the forest canopy, we generated mixing lines (Keeling plots) for δa 13CO2, δa C18O16O and δa H2 18O, to derive the(More)
C(4) photosynthesis involves alterations to leaf development, cell biology and biochemistry. Different lineages of C(4) plants use varying mechanisms to generate the C(4) pathway. Although the biochemistry of C(4) photosynthesis was described around 20 years ago, the phylogenetic distance between Arabidopsis and the traditional C(4) models has not(More)